The invention relates to a closing cap, particularly for the radiator of a motor vehicle, comprising an excess-pressure valve and a sub-pressure valve mounted in a valve seat plate, with the sub-pressure valve including a valve disc which is secured to a valve tappet extending through the valve seat and which cooperates with the sub-pressure valve seat of the valve seat plate.
Such pressure-type caps are known per se. Due to the construction of the excess-pressure valve of prior art caps, however, their locking member tends to occupy an oblique position so that varying pressures are obtained in a system equipped with such a closing cap, for example, in the cooling system of a motor vehicle. Since a valve stem is used for the valve disc of the excess-pressure valve, the cross-section area of flow is unfavorable and the needed weight rate of the fluid flow is not always ensured. On the other hand, for various reasons, the size of the prior art closing cap cannot either, or can hardly be, enlarged. Another drawback is that, in a series of locking caps of this kind, the pressure to which at least the excess-pressure valve is responsive, varies so that upon an exchange of the cap, a higher or lower pressure in the radiator, etc. may be obtained. As a rule, and in general, not only in prior art closing caps, the sub-pressure valve is less problematic.
The invention is directed to a closing cap in accordance with the preamble of claim 1 in which the excess pressure valve closes securely under any circumstances and always ensures the needed weight rate of the fluid flow within the provided range.
To this end the invention provides the features set forth in the characterizing part of claim 1. Since a valve stem is omitted, no angular tilt can occur and a perfect closing is ensured. In addition, the space formerly occupied by a valve stem is now available for a larger, thus more favorable, cross-sectional area of flow. Consequently, the excess-pressure valve does not tend to a slow and uncontrolled opening, and the full cross-sectional area of flow is instantly free at an excess pressure, which is required particularly if a closing cap for a motor vehicle radiator is concerned.
In a development of the invention, it is provided that the retaining member is formed with a locking flange cooperating with a locking groove of the valve seat plate, and that the aperture is provided in the bottom of the retaining member. The fluid under excess pressure which penetrated into the excess-pressure valve through an aperture in the valve seat plate, flows out through this aperture. Because of the locking connection between the retaining member and the valve seat plate, the excess-pressure valve can very quickly and easily be mounted. It is also rapidly accessible at any time. In another development, the invention provides that the aperture is rimmed on its inward side with a toroidal flange serving as a centering shoulder for the associated end of the closing spring which is designed as a helical compression spring. This ensures that the aperture is continually available without any limitation and is not even partly covered by the spring. Moreover, the centering of this spring ensures a quite satisfactory contact pressure between the valve disc and its seat, and a centric force application to the valve disc in the open position.
According to an advantageous development of the invention, the excess-pressure valve seat is provided at the bottom of a cup-shaped, box-like extension of the valve seat plate, projecting in the direction of the rim of the closing cap, and a plurality of strips or the like, for guiding the valve disc having a circular circumference, is provided inside the wall of the box-like extension and, particularly, regularly distributed over the circumference. In their circumferential direction, the guide strips are of a width such that they both ensure a guidance and leave sufficiently large flow channels. The total cross-sectional area of the flow channels between the guide strips should be at least equal to the inlet area of the excess-pressure valve. The flow through the channels then also contributes to a satisfactory centering of the valve disc. In addition, experience has shown that this design of the excess pressure valve ensures a complete opening of the valve in the shortest time so that it is superior to any other construction.
Advantageously, the valve disc is provided, on either of its sides, with a stud-shaped of tubular projection, with a seal ring being clamped onto one of the projections, and the fittingly shaped end of the closing spring being clamped to the other projection. This facilitates the assembly of the excess-pressure valve since the closing spring and the seal ring can be put in place on the valve disc in advance and then inserted as a unit.
As mentioned, prior art closing caps have the disadvantage that, within a series, the values, particularly of the actuating pressure of the excess-pressure valve, may vary considerably from each other, and that with the given tolerances, the major part does not satisfy the requirements on dimension. A rework, if at all possible, is very expensive. Therefore, the invention is further directed to a closing cap with which the values required for the opening pressure of the excess-pressure valve can better be ensured. For this purpose, in accordance with a further development of the invention, the projection of the valve disc is provided with at least one engaging or receiving element for a driving tool engageable therewith, and the retaining member is provided, particularly on its centrally apertured cup bottom, with a stop for the open spring end bearing thereon, with the engaging or receiving element being located substantially in alignment with the aperture of the retaining member. The engaging or receiving element of the valve disc can be reached by a proper tool through the aperture of the retaining member. The valve disc can thus be turned about its central axis by the tool from the outside. Since the respective end of the closing spring is clamped to the valve disc, the spring turns along. The upper spring end bearing against the stop is free. Therefore, the contact pressure between the valve disc and its seat only depends on what portion of the last turn of the spring at the free end thereof bears against the stop. If the closing spring is now turned through the valve disc by the tool, this pressure can be increased or reduced. The actuating pressure of the excess-pressure valve can thus be adjusted in a particularly simple way and expeditiously, and a relatively simple tool can be used. For example, the tool may be a pipe with a slotted end, with a cross-bar at its other end. In such an instance, it is particularly advantageous if with a tubular projection of the valve disc receiving the associated end of the spring, two engaging elements offset through 180.degree. are provided in the interior of the tubular projection.
Still another advantageous development of the invention is that the bottom facing the closing spring of the retaining member of the excess-valve is provided with a helicoidal surface engaging with a mating helicoidal surface of a setting member which is received for rotary motion in the retaining member and bears against the associated end of the spring, and is provided with an engaging element through which it can be rotated, or with a receiving part for such an element. In this embodiment, the spring end associated with the retainingmember, does not bear thereagainst directly, but through the special setting member. This member is substantially tubular and has an outwardly projecting flange on which the helicoidal mating surface is provided. At an excess pressure, the escaping fluid flows through this setting member which is received by its outer circumference in the aperture of the retaining member. In addition, the setting member is provided, particularly on its somewhat outwardly projecting end, with an element for engaging an actuating tool, more particularly with a hexagonal recess. The setting member may also be equipped directly with a handle. The extension and pitch of the helicoidal surfaces determine the range within which the closing spring can be tensioned or relieved. The helicoidal surface may extend through 360.degree. , for example, so that upon fully turning the closing spring, the spring is relieved by an amount corresponding to the pitch of the helicoidal surface. An unintentional relief caused by the setting member turning back can easily be prevented by choosing an appropriate material, pitch, or friction in the seat. It is also possible, in accordance with a further development of the invention, to provide that the helicoidal surfaces are stepped or have saw toothlike faces, so that any particular measure at other locations preventing the rotation may be omitted. With such a design, the setting occurs in steps, which is by no means disadvantageous since the tolerance range is sufficiently wide and, as a rule, the adjustment requires turning through more than one step.
Another advantageous embodiment of the invention is that the projecting end of the valve tappet of the sub-pressure valve is provided with an enlarged head, preferably of conical shape, forming a bearing shoulder for the smaller-base end of a frustoconical helical compression spring whose larger-base end bears against the valve seat plate. Making the valve tappet and valve disc in one piece not only reduces expenses but also allows more precision in manufacture than if two pieces connected with each other are used, as in the prior art.